Aviation Weather Services – Forecast Text Products
Area Forecasts (FA)
The NWS issues Area Forecasts (FA) to provide an overview of regional weather conditions that could impact aviation operations in the U.S. and adjacent coastal waters. Area forecasts are issued by the following offices for the following areas:
- • The Aviation Weather Center (AWC)
o Conterminous U.S. and adjacent coastal waters (CONUS)
o Gulf of Mexico
o Caribbean Sea and north Atlantic Ocean - • The Alaskan Aviation Weather Unit (AAWU) o Alaska and adjacent coastal waters
- • WFO Honolulu, Hawaii o Hawaii and adjacent coastal waters
They are all available on the Aviation Weather Center (AWC) web site.
CONUS (FAUS) and Hawaii (FAHW) Area Forecasts A CONUS and Hawaii Area Forecast (FA) describe, in abbreviated language, specified en route weather phenomena below FL450. To understand the complete weather picture, the FA must be used in conjunction with the AIRMETs and SIGMETs. Together, they are used to determine forecast en route weather and to interpolate conditions at airports for which no Terminal Aerodrome Forecasts (TAFs) are issued.
Hazardous weather (e.g., IFR, icing, turbulence, etc.) meeting AIRMET or SIGMET criteria is not forecast in the CONUS or Hawaii FA. Valid AIRMETs and SIGMETs must be used in conjunction with the FA to determine hazardous weather information for the flight.
An Area Forecast (FA) provides an overview of regional weather conditions that could impact aviation operations in the U.S. and adjacent coastal waters. The Area Forecast does not include forecast for IFR conditions so the Area Forecast must be used in conjunction with SIGMETs and AIRMETs. Each FA contains a precautionary statement, prior to the synopsis, saying SEE AIRMET SIERRA followed by a reminder of what thunderstorm activity implies and a reference to how heights not reported in MSL are denoted. This is not a reference to a specific AIRMET but a reminder the FA does not include forecasted IFR conditions.
Height Reference
All heights are referenced to Mean Sea Level (MSL) except when prefaced by AGL, CIG or CEILING. Tops are always referenced to MSL.
Format
The FA is an 18 hour forecast composed of the following 4 sections: communication and product header, precautionary statements, synopsis and visual flight rules (VFR) clouds and weather forecast.
VFR clouds and Weather (CLDS/WX)
The VFR CLDS/WX section (Figure 7-6) describes conditions consisting of MVFR cloud ceilings (1,000 to 3,000 feet AGL), MVFR obstructions to visibility (3-5 statute miles), and any other significant VFR clouds (bases at or below FL180) or VFR precipitation. The CLDS/WX section also includes widespread sustained surface winds of 20 knots or greater. Occasionally, IFR conditions may be forecast in the Hawaii FA as IFR conditions may not reach AIRMET geographical coverage criteria.
This section contains a 12-hour forecast, followed by a 6-hour categorical outlook of IFR, MVFR and/or VFR, giving a total forecast period of 18 hours. In the CONUS, the CLDS/WX section is divided into regions with generally uniform weather conditions. These divisions may be by geographical regions (e.g., LM – Lake Michigan) or states using their 2-letter designators (e.g. ND – North Dakota).
Issuance
The CONUS FAUSs are issued three times daily for each of six areas.
Other FAs
Gulf of Mexico Area Forecast (FAGX)
The Gulf of Mexico FA is an overview of weather conditions that could impact aviation operations over the northern Gulf of Mexico (Figure 7-7). It serves as a flight-planning and weather briefing aid and describes weather of significance to general aviation (GA), military and helicopter operations. The FAGX is a 24 hour forecast product with the synopsis valid the entire 24 hour period, the forecast section valid the first 12 hours, and the outlook section is valid the last 12 hours.
Caribbean Area Forecast (FACA)
The Caribbean FA is an overview of weather conditions that could impact aviation operations over the Caribbean Sea and adjacent landmasses and islands and the southwestern portions of the New York Oceanic FIR (Figure 7-8). Specifically, it covers the Atlantic south of 32N and W of 57W, the Caribbean from surface to FL240 (approximately 400 millibars).
The synopsis and forecast sections are valid for 12 hours each, with the outlook valid for 12 hours beyond the synopsis and forecast section valid period. In this form, it serves as a flight planning and weather briefing aid for general aviation pilots, and civil and military aviation operations.
Alaska Area Forecast
The Alaskan FAs contain an overview of weather conditions that could impact aviation operations over Alaska and it coastlines. The Alaskan FAs contain a short synopsis for the entire area and a forecast for each of a specified number of aviation zones (Figure 7-9). The valid period of the synopsis and flight precautions section is 12 hours. The outlook section is for eighteen (18) hours beyond the forecast valid period.
Terminal Aerodrome Forecast (TAF)
A Terminal Aerodrome Forecast (TAF) is a concise statement of the expected meteorological conditions significant to aviation for a specified time period within five statute miles (SM) of the center of the airport’s runway complex (terminal). The TAFs use the same weather codes found in METAR weather reports (Section 2) and can be viewed on the National Weather Service (NWS) Aviation Digital Data Service (ADDS) web site at: http://adds.aviationweather.noaa.gov/tafs/.
Type of Report (TAF or TAF AMD)
The report-type header always appears as the first element in the TAF and is produced in two forms: a routine forecast, TAF, and an amended forecast, TAF AMD.
TAFs are amended whenever they become, in the forecaster’s judgment, unrepresentative of existing or expected conditions, particularly regarding those elements and events significant to aircraft and airports. An amended forecast is identified by TAF AMD (in place of TAF) on the first line of the forecast text.
Vicinity (VC)
In the United States, vicinity (VC) is defined as a donut-shaped area between 5 and 10SM from the center of the airport’s runway complex. The FAA requires TAFs to include certain meteorological phenomena which may directly affect flight operations to and from the airport. Therefore, NWS TAFs may include a prevailing condition forecast of fog, showers and thunderstorms in the airport’s vicinity. A prevailing condition is defined as a greater than or equal to 50% probability of occurrence for more than ½ of the sub-divided forecast time period. VC is not included in TEMPO or PROB groups.
Issuance Scheduled TAFs prepared by NWS offices are issued four times a day, every six (6) hours, according to the following schedule: 0000Z, 0600Z, 1200Z, 1800Z.
International Aviation Route Forecasts (ROFOR)
International ROFORs are prepared and issued several hours in advance of regularly scheduled flights. The only NWS office which routinely issues ROFORs is the Weather Forecast Office (WFO) in Honolulu in its capacity as a Meteorological Watch Office (MWO) for ICAO, for routes within its area of responsibility that are underserved by conventional aviation forecasts and products.
Wind and Temperature Aloft Forecast (FB)
Wind and Temperature Aloft Forecasts (FB) are computer prepared forecasts of wind direction, wind speed, and temperature at specified times, altitudes, and locations. Forecasts are based on the North American Mesoscale (NAM) forecast model run. FBs are available on the Aviation Weather Center (AWC) web site.
Forecast Altitudes
Altitudes up to 15,000 feet are referenced to Mean Sea Level (MSL). Altitudes at or above 18,000 feet are references to flight levels (FL).
Wind forecasts are not issued for altitudes within 1,500 feet of a location’s elevation. Temperature forecasts are not issued for altitudes within 2,500 feet of a location’s elevation. Forecasts for intermediate levels are determined by interpolation.
Format
The symbolic form of the forecasts is DDff+TT in which DD is the wind direction, ff the wind speed, and TT the temperature.
Wind direction is indicated in tens of degrees (two digits) with reference to true north and wind speed is given in knots (two digits). Light and variable wind or wind speeds of less than 5 knots are expressed by 9900. Forecast wind speeds of 100 through 199 knots are indicated by adding 100 to the speed and subtracting 50 from the coded direction.
Temperature is indicated in degrees Celsius (two digits) and is preceded by the appropriate algebraic sign for the levels from 6,000 through 24,000 feet. Above 24,000 feet, the sign is omitted since temperatures are always negative at those altitudes.
The product header includes the date and time observations were collected, the forecast valid date and time, and the time period during which the forecast is to be used.
Issuance
The NWS National Centers for Environmental Prediction (NCEP) produces scheduled Wind and Temperature Aloft Forecasts (FB) four (4) times daily for specified locations in the Continental United States (CONUS), the Hawaiian Islands, Alaska and coastal waters, and the western Pacific Ocean. Amendments are not issued to the forecasts.